President Obama has written five letters to Congress informing lawmakers of American military actions against the Islamic State of Iraq and Syria. The first four relied entirely on the president’s constitutional authority to conduct foreign policy and command U.S. military forces. In his latest letter Tuesday, however, Obama cited two additional authorities: the authorizations Congress gave George W. Bush to use military force, first after the September 11 attacks and later for the 2003 invasion of Iraq. Obama, of course, was a fierce critic of the Iraq war and has actually advocated repeal of the Iraq authorization — before he decided to use it for his present purposes.